Motorbike Tyre Size Explained: What Do the Numbers Mean?

Have you ever looked at the side of your motorbike tyre and noticed numbers such as 90/90-14 or 100/80-14?

They aren’t random numbers. They provide important information about the tyre’s dimensions and compatibility with the wheel.

Having a motorbike tyre size explained can help you understand what you’re riding on and why fitting the correct tyre matters for handling, comfort, and everyday riding.

Let’s break down a common example—90/90-14—one number at a time.

How to Read a Motorbike Tyre Size

Before getting into the details, here’s the simple version.

For a tyre marked 90/90-14:

• 90 = approximate tyre width in millimetres
• 90 = aspect ratio
• 14 = wheel diameter in inches

Each measurement describes something different.

Once you’ve seen a motorbike tyre size explained this way, those numbers become much easier to understand.

1. First Number: Motorbike Tyre Width

Let’s start with our example:

90/90-14

The first number—90—indicates the tyre’s nominal section width in millimetres.

In simple terms, the tyre is approximately 90 mm wide.

Another tyre marked 100/80-14 has a nominal width of approximately 100 mm.

However, don’t assume a wider tyre is automatically better.

Motorcycles are designed around particular tyre and wheel specifications. Changing the width can affect how the motorbike handles and whether the tyre has adequate clearance.

That’s why tyre width should be selected according to the appropriate specifications for the particular motorbike.

2. Second Number: Tyre Aspect Ratio

The second number represents the tyre’s aspect ratio.

For our example:

90/90-14

The second 90 means the tyre’s sidewall height is approximately 90% of its nominal width.

The calculation is:

90 mm × 90% = 81 mm

That gives an approximate sidewall height of 81 mm.

Here’s another example:

100/80-14

The tyre has a nominal width of 100 mm and an aspect ratio of 80%.

Therefore:

100 mm × 80% = 80 mm

This is an important detail when having a motorbike tyre size explained, because the second number isn’t a direct measurement in millimetres. It’s a percentage of the tyre’s width.

3. Last Number: Wheel Diameter

Now let’s look at the final number:

90/90-14

The 14 indicates the diameter of the wheel rim the tyre is designed to fit, measured in inches.

In this example, the tyre is intended for a 14-inch wheel.

This measurement is particularly important because the tyre must be compatible with the rim diameter.

You may see motorbikes using different wheel sizes depending on their design and intended purpose, so don’t assume that every tyre will fit every motorbike.

What Does M/C Mean on a Motorbike Tyre?

Numbers aren’t the only markings you may find on a tyre.

For example, you might see:

90/90-14 M/C

The M/C marking indicates that the tyre is intended for motorcycle use.

Depending on the tyre, you may also see additional letters and numbers relating to factors such as construction, load capacity, speed rating, and other specifications.

So, while having the basic motorbike tyre size explained helps you understand the main dimensions, there can be additional markings worth checking as well.

Are All Motorbike Tyre Size Formats the Same?

Not necessarily.

Motorcycle tyres can use different marking formats depending on tyre type, construction, manufacturer, and application.

For example, you may encounter markings that include letters within the tyre size.

A letter such as R commonly indicates radial construction. Other markings can provide additional information about the tyre.

This means you shouldn’t interpret every tyre marking based solely on one example.

When replacing a tyre, check the motorbike manufacturer’s specifications and the complete tyre markings rather than looking at only one number.

Does a Wider Motorbike Tyre Give More Grip?

It’s easy to assume that wider always means better, but tyre performance is more complicated than width alone.

Tyre design, compound, construction, pressure, condition, compatibility, road surface, and other factors all influence performance.

More importantly, a motorbike is designed to work with specific tyre dimensions.

Installing a wider tyre simply because you prefer the appearance can potentially change the bike’s handling characteristics or create clearance problems.

The correct tyre is more important than simply choosing the widest one available.

Why You Shouldn’t Change Motorbike Tyre Size Just for Appearance

Once they’ve had their motorbike tyre size explained, some riders may wonder whether they can simply install a wider or larger tyre.

Changing tyre dimensions can potentially affect:

• Handling
• Steering response
• Ride characteristics
• Physical clearance
• Speedometer readings on some motorcycles
• Overall performance

There may also be compatibility considerations involving the rim and surrounding motorcycle components.

For these reasons, use the tyre specifications recommended for your particular motorbike unless a qualified professional confirms that an alternative specification is appropriate.

Appearance alone isn’t a good reason to install an unsuitable tyre.

Why Correct Motorbike Tyre Size Matters

Your tyres are a critical connection between your motorbike and the road.

Correct tyre specifications contribute to predictable handling and ensure the tyre is suitable for the wheel and motorcycle it is installed on.

Incorrect sizing can potentially change the way a bike steers or handles.

Tyre size isn’t the only consideration either. Riders should also pay attention to tyre condition and appropriate inflation pressure.

If you’re unsure about a tyre specification, check the motorcycle manufacturer’s information or ask a qualified professional.

Easy Way to Remember Motorbike Tyre Numbers

Let’s return to our original example:

90/90-14

Remember it like this:

90 = tyre width

90 = sidewall aspect ratio

14 = wheel diameter

Or, even more simply:

WIDTH → RATIO → WHEEL

That’s the easiest way to remember the basic format after having a motorbike tyre size explained.

What Else Should You Check on a Motorbike Tyre?

Understanding the numbers is useful, but tyre size isn’t the only thing riders should pay attention to.

Before riding, particularly on an unfamiliar or rental motorbike, look at the tyres for obvious signs of a problem.

If you notice visible damage, unusual wear, significant loss of pressure, or the motorbike suddenly handles differently, have the issue checked rather than ignoring it.

Tyre condition can directly affect how a motorbike feels when steering and braking.

Motorbike Tyres on Rental Bikes

When renting a motorbike, you don’t necessarily need to become a tyre expert. However, understanding basic tyre markings and recognizing when something doesn’t look or feel right can still be useful.

At Jan’s Motorbike, our rental bikes are maintained for everyday commuting around Ho Chi Minh City.

Customers can also take a free test ride before deciding. This gives you an opportunity to become familiar with the motorbike’s handling, throttle, brakes, and overall riding feel.

Jan’s Motorbike rentals include:

• Motorbikes in excellent condition and ready to ride
• Complimentary helmet and phone holder
• Free test ride before you decide
• Personal group chat support throughout your rental

If you notice something unusual with the tyres, handling, or another part of your rental motorbike, contact our team through your personal support group chat.

For more advice before riding around the city, see our guide to riding safely in Ho Chi Minh City traffic.

Frequently Asked Questions

What does 90/90-14 mean on a motorbike tyre?

For a typical tyre marked 90/90-14, 90 represents the nominal tyre width in millimetres, the second 90 is the aspect ratio, and 14 indicates the wheel rim diameter in inches.

What does the second number in a motorbike tyre size mean?

The second number is the aspect ratio. It represents the sidewall height as a percentage of the tyre’s nominal width. For a 90/90 tyre, the sidewall height is approximately 90% of 90 mm.

What does M/C mean on a tyre?

M/C indicates that the tyre is intended for motorcycle use. You may find this marking alongside the tyre dimensions and other specifications.

Can I install a wider tyre on my motorbike?

Don’t assume a wider tyre is suitable simply because it fits visually or looks better. Different dimensions can affect clearance and handling. Follow the motorbike manufacturer’s specifications or consult a qualified professional before changing tyre size.

Does a wider motorbike tyre automatically provide better grip?

No. Grip depends on numerous factors, including tyre design, compound, construction, condition, pressure, road conditions, and compatibility with the motorcycle. Width alone does not determine whether a tyre is better.

How do I know the correct tyre size for my motorbike?

Check the tyre specifications provided by the motorcycle manufacturer. If you’re uncertain, consult a qualified motorcycle or tyre professional rather than choosing a size based solely on appearance.

Final Thoughts

With a motorbike tyre size explained, markings such as 90/90-14 become much less mysterious.

The first number indicates the tyre’s nominal width, the second describes its aspect ratio, and the final number tells you the wheel diameter it is designed to fit.

Just remember:

WIDTH → RATIO → WHEEL

And while understanding tyre numbers is useful, choosing the correct specification matters more than choosing a tyre because it looks wider or sportier.

Use the appropriate tyre for your motorbike, pay attention to its condition, and get professional advice whenever you’re unsure.

Contact JAN’S MOTORBIKE: +84909 29 0078 (WhatsApp,Zalo)

Find Us: 5, 5th Street An Phu Ward, District 2 

Check for full available motorbike HERE.